Singlet oxygen had heretofore been studied intensively. See, for example, "Singlet Molecular Oxygen" edited by A. P. Schaap, (Dowden, Hutchinson and Ross), 1976; and "International Conference on Singlet Molecular Oxygen and Its Role in Environmental Sciences," Annals of the New York Academy of Sciences, Vol. 171, Act. I, pages 1-302 (1970).
In addition to use in scientific or research-related fields, singlet oxygen has been proposed for a number of applications. For example, singlet oxygen chemically pumps iodine gas lasers. Applications of the latter and other types, however, require substantial volumes and concentrations of singlet oxygen.
Convenient and efficient production of singlet oxygen has yet to be accomplished in the art. Although certain solvent based reactions generate significant amounts of singlet oxygen, such processes possess a number of inherent limitations. The liquid solvent, as well as cryogenic traps and the like for removal of coincidentally produced impurities, tend to quench the singlet oxygen as the latter is produced and consequently limit efficiency of these generators. Moreover, since the by-products of these solvent based reactions are not regenerated into the initial reactants, the utility of these systems is further compromised. Furthermore, use of the aforementioned solvent based reactions can be harardous and require massive apparatus.
It has been recognized that irradiation of gaseous ground state oxygen with laser, microwave or other electromagnetic radiation converts ground state oxygen to singlet oxygen. But these techniques do not store singlet oxygen and, moreover, do not generate singlet oxygen in desired quantities and at sufficient rates.
Solid phase generators containing temporarily bound singlet oxygen avoid certain of these problems of quenching, bulky apparatus and storage discussed above. Murray et al, "Singlet Oxygen Sources in Ozone Chemistry, Chemical Oxygenations Using Adducts Between Phosphite Esters and Ozone", J. Amer. Chem. Soc. 91 (19), 5358-64 (1961) suggests that singlet oxygen can be generated directly into the gas phase from solid phosphite ester and ozone adduct dispersions. But the phosphite ester and ozone adducts are not regenerable and require extremely low temperatures for storage.